The ability to think through causes and effects is a key to success in many college courses, jobs, and everyday situations. Daily we puzzle over the causes of, or reasons for, events: What caused one brother to drop out of school and another to succeed brilliantly? What causes Jenine's asthma attacks? Why did the stock market plunge 300 points?

Effects are the results of a cause or causes. Does playing violent computer games affect a child's behavior? What are the effects of being a twin, keeping a secret, or winning the lottery?

Most events worth examining have complex, not simple, causes and effects. That is, they may have several causes and several effects. Certainly, in many fields, questions of cause and effect challenge even the experts: What will be the long-term effects of the breakup of the former Soviet Union? What causes the HIV virus to disappear from the blood of some infected babies? (This one answer could help save millions of lives.)